The present invention relates to a family of purified proteins, termed BMP-6 proteins (wherein BMP is bone morphogenic protein), which exhibit the ability to induce cartilage and/or bone formation and processes for obtaining them. These proteins may be used to induce bone and/or cartilage formation and in wound healing and tissue repair.
The invention provides purified human BMP-6 proteins, substantially free from other proteins with which they are co-produced. The BMP-6 proteins of the invention are characterized by an amino acid sequence comprising acid #412 to amino acid #513 set forth in Table III. The amino acid sequence from amino acid #412 to #513 is encoded by the DNA sequence of Table III from nucleotide #1393 to nucleotide #1698. These proteins may be further characterized by an apparent molecular weight of 28,000-30,000 daltons as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Under reducing conditions in SDS-PAGE the protein electrophoreses with a molecular weight of approximately 14,000-20,000 daltons. It is contemplated that these proteins are capable of stimulating promoting, or otherwise inducing cartilage and/or bone formation.
The invention further provides bovine BMP-6 proteins characterized by the amino acid sequence comprising amino acid #121 to amino acid #222 set forth in Table II. The amino acid sequence from #121 to #222 is encoded by the DNA sequence of Table II from nucleotide #361 to #666 of Table II. These proteins may be further characterized by an apparent molecular weight of 28,000-30,000 daltons as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Under reducing conditions in SDS-PAGE the protein electrophoreses with a molecular weight of approximately 14,000-20,000 daltons. It is contemplated that these proteins are capable of inducing cartilage and/or bone formation.
Human BMP-6 proteins of the invention are produced by culturing a cell transformed with a DNA sequence comprising nucleotide #1393 to nucleotide #1698 as shown in Table III or a substantially similar sequence, recovering and purifying from the culture medium a protein comprising amino acid #412 to amino acid #513 or a substantially similar sequence.
Bovine proteins of the invention may be produced by culturing a cell transformed with a DNA comprising nucleotide #361 through nucleotide #666 as set forth in Table II or a substantially similar sequence and recovering and purifying from the culture medium a protein comprising amino acid #121 to amino acid #222 as set forth in Table II.
The invention further provides a method wherein the proteins described above are utilized for obtaining related human protein/s or other mammalian cartilage and/or bone formation protein/s. Such methods are known to those skilled in the art of genetic engineering. One method for obtaining such proteins involves utilizing the human BMP-6 coding sequence or a portion thereof from nucleotide #160-#1698 to design probes for screening human genomic and/or cDNA libraries to isolate human genomic and/or cDNA sequences. Additional methods within the art may employ the bovine and human BMP-6 proteins of the invention to obtain other mammalian BMP-6 cartilage and/or bone formation proteins. Having identified the nucleotide sequences, the proteins are produced by culturing a cell transformed with the nucleotide sequence. This sequence or portions thereof hybridizes under stringent conditions to the nucleotide sequence substantially as shown in Table II comprising nucleotide #1 to nucleotide #666 or the nucleotide sequence or portions thereof substantially as shown in Table III comprising nucleotide #160 to #1698 and encodes a protein exhibiting cartilage and/or bone formation activity. The expressed protein is recovered and purified from the culture medium. The purified BMP-6 proteins of the invention are substantially free from other proteinaceous materials with which they are co-produced, as well as from other contaminants.
The BMP-6 proteins of the invention are further characterized by the ability to promote, stimulate or otherwise induce the formation of cartilage and/or bone. It is further contemplated that the ability of these proteins to induce the formation of cartilage and/or bone is exhibited by the ability to demonstrate cartilage and/or bone formation activity in the rat bone formation assay described below. It is further contemplated that the proteins of the invention demonstrate activity in this rat bone formation assay at a concentration of 10 xcexcg-500 xcexcg/gram of bone formed. More particularly, it is contemplated these proteins may be characterized by the ability of 1 xcexcg of the protein to score at least +2 in the rat bone formation assay described below using either the original or modified scoring method.
Another aspect of the invention provides pharmaceutical compositions containing a therapeutically effective amount of a protein of the invention in a pharmaceutically acceptable vehicle or carrier. These compositions of the invention may be used to induce bone and/or cartilage formation. These compositions may also be used for wound healing and tissue repair. Further compositions of the invention may include, in addition to a BMP-6 protein, at least one other therapeutically useful agent such as the proteins designated BMP-1, BMP-2A and -2B, BMP-3, BMP-5, and BMP-7 disclosed respectively in co-owned U.S. patent applications Ser. No. 179,101, Ser. No. 179,100, and Ser. No. 179,197, Ser. No. 437,409, Ser. No. 438,919. Other therapeutically useful agents include growth factors such as epidermal growth factor (EGF), fibroblast growth factor (FGF), transforming growth factors (TGF-xcex1 and TGF-xcex2) and platelet derived growth factor (PDGF). The compositions of the invention may also include an appropriate matrix, for instance, for delivery and support of the composition and/or providing a surface for bone and/or cartilage growth.
The compositions may be employed in methods for treating a number of bone and/or cartilage defects, and periodontal disease. They may also be employed in methods for treating various types of wounds and in tissue repair. These methods, according to the invention, entail administering to a patient needing such bone and/or cartilage formation, wound healing or tissue repair, a therapeutically effective amount of a BMP-6 protein of the invention in a pharmaceutically acceptable vehicle or carrier including a martrix. These methods may also entail the administration of a BMP-6 protein in conjunction with at least one of the xe2x80x9cBMPxe2x80x9d proteins disclosed in the co-owned applications described above. In addition, these methods may also include the administration of a protein of the invention with other growth factors including EGF, FGF, TGF-xcex1, TGF-xcex2, and PDFG.
Still a further aspect of the invention are DNA sequences coding for expression of a protein of the invention. Such sequences include the sequence of nucleotides in a 5xe2x80x2 to 3xe2x80x2 direction illustrated in Table II or Table III or DNA sequences which hybridize under stringent conditions with the DNA sequence of Table II or Table III and encode a protein demonstrating ability to induce cartilage and/or bone formation. Such ability to induce cartilage and/or bone formation may be demonstrated in the rat bone formation assay described below. It is contemplated that these proteins demonstrate activity in this assay at a concentration of 10 xcexcg-500 xcexcg/gram of bone formed. More particularly, it is contemplated that these proteins demonstrate the ability of 1 xcexcg of the protein to score at least +2 in the rat bone formation assay using either the original or modified scoring method. Allelic or variations as described herein below of the sequences of Table II and III, whether such nucleotide changes result in changes in the peptide sequence or not, are also included in the present invention.
A further aspect of the invention provides vectors containing a DNA sequence as described above in operative association with an expression control sequence therefor. These vectors may be employed in a novel process for producing a protein of the invention in which a cell line transformed with a DNA sequence directing expression of a protein of the invention in operative association with an expression control sequence therefor, is cultured in a suitable culture medium and a protein of the invention is isolated and purified therefrom. This claimed process may employ a number of known cells, both prokaryotic and eukaryotic, as host cells for expression of the polypeptide.
Other aspects and advantages of the present invention will be apparent upon consideration of the following detailed description and preferred embodiments thereof.
The purified human BMP-6 proteins of the invention are characterized by an amino acid sequence comprising amino acid #412 to #513 as set forth in Table III. In one embodiment a BMP-6 protein of the invention comprises amino acid #388 to #513 of Table III. In a further embodiment the BMP-6 protein comprises amino acid #382 to #513 of Table III.
The purified BMP-6 human cartilage/bone proteins of the present invention may be produced by culturing a host cell transformed with a DNA sequence comprising nucleotide #1393 to nucleotide #1698 as set forth in Table III or substantially homologous sequences operatively linked to a heterologous regulatory control sequence and recovering, isolating and purifying from the culture medium a protein comprising amino acid #412 to amino acid #513 as set forth in Table III or a substantially homologous sequence.
In another embodiment, purified human BMP-6 proteins may be produced by culturing a host cell transformed with a DNA sequence comprising nucleotide #1321 to #1698 as set forth in Table III or substantially homologous sequences operatively linked to a heterologous regulatory control sequence and recovering and purifying from the culture medium a protein comprising amino acid #388 to #513 asset forth in Table III or a substantially homologous sequence.
In another embodiment, purified human BMP-6 proteins may be produced by culturing a host cell transformed with a DNA sequence comprising nucleotide #1303 to #1698 as set forth in Table III or substantially homologous sequences operatively linked to a heterologous regulatory control sequence and recovering and purifying from the culture medium a protein comprising amino acid #382 to #513 as set forth in Table III or a substantially homologous sequence.
The purified human BMP-6 proteins are substantially free from other proteinaceous materials with which they are co-produced, as well as-from other contaminants.
Purified BMP-6 bovine cartilage/bone protein of the present invention are produced by culturing a host cell transformed with a DNA sequence comprising nucleotide #361 to nucleotide #666 as set forth in Table II or substantially homologous sequences and recovering from the culture medium a protein comprising amino acid #121 to amino acid #222 as set forth in Table II or a substantially homologous sequence. In another embodiment the bovine protein is produced by culturing a host cell transformed with a sequence comprising nucleotide #289 to #666 of Table II and rcovering and purifying a protein comprising amino acid #97 to amino acid #222. The purified BMP-6 bovine proteins are substantially free from other proteinaceous materials with which they are co-produced, as well as from other contaminants.
These proteins of the invention may be further characterized by the ability to demonstrate cartilage and/or bone formation activity. This activity may be demonstrated, for example, in the rat bone formation assay as described in Example III. It is further contemplated that these proteins demonstrate activity in the assay at a concentration of 10 xcexcg-500 xcexcg/gram of bone formed. The proteins may be further characterized by the ability of 1 xcexcg to score at least +2 in this assay.
BMP-6 proteins may be further characterized by an apparent molecular weight of 28,000-30,000 daltons as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Under reducing conditions in SDS-PAGE, the protein electrophoreses with a molecular weight of approximately 14,000-20,000 daltons.
The proteins provided herein also include factors encoded by the sequences similar to those of Table II and Table III but into which modifications are naturally provided (e.g. allelic variations in the nucleotide sequence which may result in amino acid changes in the polypeptide) or deliberately engineered. Similarly, synthetic polypeptides which wholly or partially duplicate continuous sequences of the amino acid residues of Table II or Table III are encompassed by the invention. These sequences, by virtue of sharing primary, secondary, or tertiary structural and conformational characteristics with other cartilage/bone proteins of the invention may possess bone and/or cartilage growth factor biological properties in common therewith. Thus, they may be employed as biologically active substitutes for naturally-occurring proteins in therapeutic processes.
Other specific mutations of the sequences of the proteins of the invention described herein may involve modifications of a glycosylation site. These modifications may involve O-linked or N-linked glycosylation sites. For instance, the absence of glycosylation or only partial glycosylation at the asparagine-linked glycosylation sites results from amino acid substitution or deletion at the asparagine-linked glycosylation recognition sites present in the sequences of the proteins of the invention, for example, as shown in Table II or Table III. The asparagine-linked glycosylation recognition sites comprise tripeptide sequences which are specifically recognized by appropriate cellular glycosylation enzymes. These tripeptide sequences are either asparagine-X-threonine or asparagine-X-serine, where X is usually any amino acid. A variety of amino acid substitutions or deletions at one or both of the first or third amino acid positions of a glycosylation recognition site (and/or amino acid deletion at the second position). results in non-glycosylation at the modified tripeptide sequence. Expression of such altered nucleotide sequences produces variants which are not glycosylated at that site.
The present invention also encompasses the novel DNA sequences, free of association with DNA sequences encoding other proteinaceous materials, and coding on expression for the proteins of the invention. These DNA sequences include those depicted in Tables II and III in a 5xe2x80x2 to 3xe2x80x2 direction or portions thereof. Further included are those sequences which hybridize under stringent hybridization conditions [see, T. Maniatis et al, Molecular Cloning (A Laboratory Manual), Cold Spring Harbor Laboratory (1982), pages 387 to 389] to the DNA sequence of Table II or Table III and demonstrate cartilage and/or bone formation activity. Such cartilage and/or bone formation activity may be in the rat bone formation assay. An example of one such stringent hybridization condition is hybridization at 4xc3x97 SSC at 65xc2x0 C., followed by a washing in 0.1xc3x97 SCC at 65xc2x0 C. for an hour. Alternatively, an exemplary stringent hybridization condition is in 50% formamide, 4xc3x97 SCC at 42xc2x0 C.
Similarly, DNA sequences which encode proteins similar to the protein encoded by the sequence of Table II or Table III, but which differ in codon sequence due to the degeneracies of the genetic code or allelic variations (naturally-occurring base changes in the species population which may or may not result in an amino acid change) also encode the proteins of the invention described herein. Variations in the DNA sequences of Table II and Table III which are caused by point mutations or by induced modifications (including insertion, deletion, and substitution) to enhance the activity, half-life or production of the polypeptides encoded thereby are also encompassed in the invention.
In a further aspect, the invention provides a method for obtaining related human proteins or other mammalian BMP-6 proteins. One method for obtaining such proteins entails, for instance, utilizing the human BMP-6 coding sequence disclosed herein to probe a human genomic library using standard techniques for the human gene or fragments thereof. Sequences thus identified may also be used as probes to identify a human cell line or tissue which synthesizes the analogous cartilage/bone protein. A cDNA library is synthesized and screened with probes derived from the human or bovine coding sequences. The human sequence thus identified is transformed into a host cell, the host cell is cultured and the protein recovered, isolated and purified from the culture medium. The purified protein is predicted to exhibit cartilage and/or bone formation activity. This activity may be demonstrated in the rat bone formation assay of Example III.
Another aspect of the present invention provides a novel method for producing the proteins of the invention. This method involves culturing a suitable cell line, which has been transformed with a DNA sequence coding for expression of a protein of the invention, under the control of known regulatory sequences. Regulatory sequences include promoter fragments, terminator fragments and other suitable sequences which direct the expression of the protein in an appropriate host cell. Methods for culturing suitable cell lines are within the skill of the art. The transformed cells are cultured and the BMP-6 proteins expressed thereby are recovered and purified from the culture medium using purification techniques, known to those skilled in the art.
The purified BMP-6 proteins are substantially free from other proteinaceous materials with which they are co-produced, as well as other contaminants. Purified BMP-6 proteins of the invention are substantially free from materials with which the proteins of the invention exist in nature.
Suitable cells or cell lines may be mammalian cells, such as Chinese hamster ovary cells (CHO). The selection of suitable mammalian host cells and methods for transformation, culture, amplification, screening and product production and purification are known in the art. See, e.g., Gething and Sambrook, Nature, 293:620-625 (1981), or alternatively, Kaufman et al, Mol. Cell. Biol., 5(7):1750-1759 (1985) or Howley et al, U.S. Pat. No. 4,419,446. Other suitable To mammalian cell lines are the monkey COS-1 cell line and the CV-1 cell line.
Bacterial cells may also be suitable hosts. For example, the various strains of E. coli (e.g., HB101, MC1061) are well-known as host cells in the field of biotechnology. Various strains of B. subtilis, Pseudomonas, other bacilli and the like may also be employed in this method.
Many strains of yeast cells known to those skilled in the art may also be available as host cells for expression of the polypeptides of the present invention. Additionally, where desired, insect cells may be utilized as host cells in the method of the present invention. See, e.g. Miller et al, Genetic Engineering, 8:277-298 (Plenum Press 1986) and references cited therein.
Another aspect of the present invention provides vectors for use in the method of expression of the proteins of the invention. Preferably the vectors contain the full novel DNA sequences described above which code for the novel BMP-6 proteins of the invention. Additionally the vectors also contain appropriate expression control sequences permitting expression of the protein sequences. Alternatively, vectors incorporating modified sequences as described above are also embodiments of the present invention and useful in the production of the proteins of the invention. The vectors may be employed in the method of transforming cell lines and contain selected regulatory sequences in operative association with the DNA coding sequences of the invention which are capable of directing the replication and expression thereof in selected host cells. Useful regulatory sequences for such vectors are known to those skilled in the art and may be selected depending upon the selected host cells. Such selection is routine and does not form part of the present invention. Host cells transformed with such vectors and progeny thereof for use in producing BMP-6 proteins are also provided by the invention.
A protein of the present invention, which induces cartilage and/or bone formation in circumstances where bone and/or cartilage is not normally formed, has application in the healing of bone fractures and cartilage defects in humans and other animals. Such a preparation employing a protein of the invention may have prophylactic use in closed as well as open fracture reduction and also in the improved fixation of artificial joints. De novo bone formation induced by an osteogenic agent contributes to the repair of congenital, trauma induced, or oncologic resection induced craniofacial defects, and also is useful in cosmetic plastic surgery. A protein of the invention may be used in the treatment of periodontal disease, and in other tooth repair processes. Such agents may provide an environment to attract bone-forming cells, stimulate growth of bone-forming cells or induce differentiation of progenitors of bone-forming cells. A variety of osteogenic, cartilage-inducing and bone inducing factors have been described. See, e.g. European patent applications 148,155 and 169,016 for discussions thereof.
The proteins of the invention may also be used in wound healing and related tissue repair. The types of wounds include, but are not limited to burns, incisions and ulcers. (See, e.g. PCT Publication WO84/01106 for discussion of wound healing and related tissue repair).
A further aspect of the invention is a therapeutic method and composition for repairing fractures and other conditions related to bone and/or cartilage defects or periodontal diseases. In addition, the invention comprises therapeutic methods and compositions for wound healing and tissue repair. Such compositions comprise a therapeutically effective amount of at least one of the BMP-6 proteins of the invention in admixture with a pharmaceutically acceptable vehicle, carrier or matrix.
It is expected that the proteins of the invention may act in concert with or perhaps synergistically with one another or with other related proteins and growth factors. Therapeutic methods and compositions of the invention therefore comprise one or more of the proteins of the present invention. Further therapeutic methods and compositions of the invention therefore comprise a therapeutic amount of at least one protein of the invention with a therapeutic amount of at least one of the other xe2x80x9cBMPxe2x80x9d proteins, BMP-1, BMP-2 (BMP-2A, BMP-2 Class I), BMP-3, BMP-4 (BMP-2B, BMP-2 Class II), BMP-5 and BMP-7, disclosed in co-owned and co-pending U.S. applications described above. Such methods and compositions of the invention may comprise proteins of the invention or portions thereof in combination with the above-mentioned xe2x80x9cIBMPxe2x80x9d proteins or portions thereof. Such combination may comprise individual separate molecules from each of the proteins or heteromolecules such as heterodimers formed by portions of the respective proteins. For example, a method and composition of the invention may comprise a BMP-6 protein of the invention or a portion thereof linked with a portion of a different xe2x80x9cBMPxe2x80x9d protein to form a heteromolecule.
Further therapeutic methods and compositions of the invention comprise the proteins of the invention or portions thereof in combination with other agents beneficial to the treatment of the bone and/or cartilage defect, wound, or tissue in question. These agents include various growth factors such as epidermal growth factor (EGF), fibroblast growth factor (FGF), platelet derived growth factor (PDGF), transforming growth factors (TGF-xcex1 and TGF-xcex2), k-fibroblast growth factor (kFGF), parathyroid hormone (PTH), leukemia inhibitory factor (LIF/HILDA/DIA), and insulin-like growth factors (IGF-I and IGF-II). Portions of these agents may also be used in compositions of the invention.
The preparation and formulation of such physiologically acceptable protein compositions, having due regard to pH, isotonicity, stability and the like, is within the skill of the art. The therapeutic compositions are also presently valuable for veterinary applications due to the apparent lack of species specificity in cartilage and bone proteins. Domestic animals and thoroughbred horses in addition to humans are desired patients for such treatment with the proteins of the present invention.
The therapeutic method includes administering the composition topically, systemically, or locally as an implant or device. When administered, the therapeutic composition for use in this invention is, of course, in a pyrogen-free, physiologically acceptable form. Further, the composition may desirably be encapsulated or injected in a viscous form for delivery to the site of cartilage and/or bone or tissue damage. Topical administration may be suitable for wound healing and tissue repair. Preferably for bone and/or cartilage formation, the composition includes a matrix capable of delivering the cartilage/bone proteins of the invention to the site of bone and/or cartilage damage, providing a structure for the developing bone and cartilage and optimally capable of being resorbed into the body. Matrices may provide slow release of the cartilage and/or bone inductive proteins proper presentation and appropriate environment for cellular infiltration. Matrices may be formed of materials presently in use for other implanted medical applications.
The choice of matrix material is based on biocompatibility, biodegradability, mechanical properties, cosmetic appearance and interface properties. The particular application of the compositions of the invention will define the appropriate formulation. Potential matrices for the compositions are biodegradable and chemically defined calcium sulfate, tricalciumphosphate, hydroxyapatite, polylactic acid and polyanhydrides. Other potential materials are biodegradable and biologically well defined, such as bone or dermal collagen. Further matrices are comprised of pure proteins or extracellular matrix components. Other potential matrices are nonbiodegradable and chemically defined, such as sintered hydroxyapatite, bioglass, aluminates, or other ceramics. Matrices may be comprised of combinations of any of the above mentioned types of material, such as polylactic acid and hydroxyapatite or collagen and tricalciumphosphate. The bioceramics may be altered in composition, such as in calcium-aluminate-phosphate and processing to alter pore size, particle size, particle shape, and biodegradability.
The dosage regimen will be determined by the attending physician considering various factors which modify the action of the proteins of the invention. Factors which may modify the action of the proteins of the invention include the amount of bone weight desired to be formed, the site of bone damage, the condition of the damaged bone, the size of a wound, type of damaged tissue, the patient""s age, sex, and diet, the severity of any infection, time of administration and other clinical factors. The dosage may vary with the type of matrix used in the reconstitution and the type or types of bone and/or cartilage proteins present in the composition. The addition of other known growth factors, such as EGF, PDGF, TGF-xcex1, TGF-xcex2, and IGF-I to the final composition, may also effect the dosage.
Progress can be monitored by periodic assessment of cartilage and/or bone growth and/or repair. The progress can be monitored, for example, using x-rays, histomorphometric determinations and tetracycline labeling.
The following examples illustrate practice of the present invention in recovering and characterizing bovine cartilage and/or bone proteins of the invention and employing. these proteins to recover the corresponding human protein or proteins and in expressing the proteins via recombinant techniques.